The body's fat cells are formed early in life and become fixed in number as you enter your teens.  After that these cells do not multiply.  As you gain weight these cells hold more fat, and as you lose weight they hold less fat. 

As your body becomes insulin resistant, it tries to protect itself from high blood sugar levels (which are toxic) by converting the excess glucose in the blood stream into tryglicerides (fat) and pushing it into the fat cells of your body.